Network Security  and  Hacking Techniques Day 5
Introduction <ul><li>Introduction </li></ul><ul><li>What is a Honeypot? </li></ul><ul><li>Value of Honeypot </li></ul><ul>...
Honeypot <ul><li>The Honepot Project is an all-volunteer, non-profit research organization  </li></ul><ul><li>Dedicated to...
Introduction <ul><li>Term originally from the military </li></ul><ul><ul><li>fake target or ambush </li></ul></ul><ul><li>...
Goal <ul><li>Primary </li></ul><ul><ul><li>an instrument for information gathering and learning. </li></ul></ul><ul><li>ot...
Honeypot (Cont…) <ul><li>1 st  Generation Honeypot </li></ul>Firewall separating the Honeynet into three different networks
Honeypot (Cont…) <ul><li>2 nd  Generation Honeypot </li></ul>
Honeypot (Cont…) <ul><li>2nd Generation (2002-) </li></ul><ul><ul><li>easier to deploy, yet more difficult to detect </li>...
Information Security-Cryptography   <ul><li>    Basic Concepts </li></ul><ul><li>    Classical Cryptosystem </li></ul><ul>...
Information Security-Cryptography   <ul><li>Definitions </li></ul><ul><li>Introduction to Crytograhpy </li></ul><ul><li>Ex...
Definitions <ul><li>Algorithm:  The set of mathematical rules used in encryption and decryption. </li></ul><ul><li>Cryptog...
Definitions (Conts…) <ul><li>Decipher:  Act of transforming data into a readable format. </li></ul><ul><li>Key:  Secret se...
Cryptography <ul><li>The most widely used tool for securing information and services is cryptography. </li></ul><ul><li>Cr...
Example Ciphers <ul><li>Caesar cipher:  each plaintext characters is replaced by a character  k  to the right. </li></ul><...
Ciphers <ul><li>For some message  M,  let’s denote the encryption of that message into cipher text as </li></ul><ul><li>E ...
Simplified Model of Symmetric Encryption
Ingredients <ul><li>Plain text </li></ul><ul><li>Encryption algorithm </li></ul><ul><li>Secret key </li></ul><ul><li>Ciphe...
Requirements for Security <ul><li>Strong encryption algorithm </li></ul><ul><ul><li>Even if known, should not be able to d...
Attacking Encryption <ul><li>Cryptanalysis </li></ul><ul><ul><li>Relay on nature of algorithm plus some knowledge of gener...
Cryptanalysis plaintext Encrypt Decrypt K e K d C = E Ke (plaintext) Invader Side information plaintext plaintext Cryptana...
Cryptanalysis <ul><li>Cryptanalysis is the science of recovering the plaintext of a message without access to the key. </l...
Encryption Algorithms <ul><li>Block cipher </li></ul><ul><ul><li>Process plain text in fixed block sizes producing block o...
Simple Block Cipher Plaintext message B 2 B 1 B 0 encrypt B 3 B 3 B 2 B 1 B 0
Problem <ul><li>If the same block is encrypted twice with the same key, the resulting ciphertext blocks are the same </li>...
Stream Ciphers <ul><li>For some applications encryption in blocks will not work </li></ul><ul><ul><li>Telephone conversati...
Stream Cipher encrypt XOR K 0 K 1 K 2 K 3 number generator keystream buffer Plaintext stream Encrypted stream
Data Encryption Standard <ul><li>US standard </li></ul><ul><li>64 bit plain text blocks </li></ul><ul><li>56 bit key </li>...
Triple DES <ul><li>ANSI X9.17 (1985) </li></ul><ul><li>Incorporated in DES standard 1999 </li></ul><ul><li>Uses 3 keys and...
Advanced Encryption Standard <ul><li>National Institute of Standards and Technology (NIST) in 1997 issued call for Advance...
AES Description <ul><li>Assume key length 128 bits </li></ul><ul><li>Input is single 128-bit block </li></ul><ul><ul><li>D...
AES Encryption and Decryption
AES Comments (1) <ul><li>Key expanded into array of forty-four 32-bit words, w[i] </li></ul><ul><ul><li>Four distinct word...
AES Comments (1) <ul><li>Simple structure </li></ul><ul><ul><li>For both encryption and decryption, cipher begins with   A...
AES Encryption Round
AES Comments (2) <ul><li>Only Add Round Key stage  uses  key </li></ul><ul><ul><li>Begin  and ends with Add Round Key stag...
Location of Encryption Devices Encryption Across a Packet Switching Network
Link Encryption <ul><li>Each communication link equipped at both ends </li></ul><ul><li>All traffic secure </li></ul><ul><...
End to End Encryption <ul><li>Encryption done at ends of system </li></ul><ul><li>Data in encrypted form crosses network u...
Key Distribution <ul><li>Question: How to deliver a shared key to 2 parties that wish to exchange data without others to s...
Automatic Key Distribution for Connection-Oriented Protocols
Automatic Key Distribution <ul><li>Session Key </li></ul><ul><ul><li>Used for duration of one logical connection </li></ul...
Message Authentication <ul><li>Protection against active attacks </li></ul><ul><ul><li>Falsification of data </li></ul></u...
Authentication Using Encryption <ul><li>Assumes sender and receiver are only entities that know key </li></ul><ul><li>Mess...
Authentication Without Encryption <ul><li>Authentication tag generated and appended to each message </li></ul><ul><li>Mess...
Message Authentication Code <ul><li>Generate authentication code based on shared key and message </li></ul><ul><li>Common ...
Message Authentication Using a Message Authentication Code
One Way Hash Function <ul><li>Accepts variable size message and produces fixed size tag (message digest) </li></ul><ul><li...
Message Authentication Using a One-Way Hash Function
Public Key Encryption <ul><li>Based on mathematical algorithms </li></ul><ul><li>Asymmetric </li></ul><ul><ul><li>Use two ...
Public-Key Cryptography
Public Key Encryption - Operation <ul><li>One key made public </li></ul><ul><ul><li>Used for encryption </li></ul></ul><ul...
Steps <ul><li>User generates pair of keys </li></ul><ul><li>User places one key in public domain </li></ul><ul><li>To send...
Digital Signature <ul><li>Sender encrypts message with their private key </li></ul><ul><li>Receiver can decrypt using send...
Signatures <ul><li>Handwritten signatures can verify that a document is </li></ul><ul><ul><li>Authentic </li></ul></ul><ul...
Digital Signatures <ul><li>Public key systems can also be used to provide message authentication: </li></ul><ul><ul><li>Th...
Digital Properties <ul><li>The properties of digital documents are different from paper documents </li></ul><ul><ul><li>We...
Message Digests <ul><li>Message digests are used to create short, fixed-length representations of longer, variable-length ...
Digests
Next Problem <ul><li>You digitally sign a document </li></ul><ul><li>Send the document to a bank </li></ul><ul><ul><li>Enc...
Certificates <ul><li>A certificate associates a public key with the real identity of an individual, server, or other entit...
Certificate Authority <ul><li>A trusted source of certificates </li></ul><ul><ul><li>Verifying certificate requests </li><...
The RSA Algorithm <ul><li>  Key Generation </li></ul><ul><li>  Select  p ,  q p  and  q  both prime,  p      q </li></ul>...
Example of RSA Algorithm
Public-Key Certificate Use
Implementing Network Security using VPNs   <ul><li>Introduction to VPNS </li></ul><ul><li>Overview of VPNs </li></ul><ul><...
What is a VPN? <ul><li>A private network constructed over a shared infrastructure </li></ul><ul><li>Virtual: not a separat...
Deploying VPNs in the 1990s <ul><li>Operational model </li></ul><ul><ul><li>PVCs overlay the shared infrastructure (ATM/Fr...
Deploying VPNs in the 21st'Century <ul><li>Uses IP infrastructure  </li></ul><ul><li>Can be,shared with Internet services ...
VPN Classification Model <ul><li>Customer-managed VPN solutions (CPE-VPNs) </li></ul><ul><ul><li>Layer 2: L2TP and PPTP </...
CPE- Based VPN’s
CPE-VPNs: L2TP and PPTP <ul><li>Application: Dial access for remote users </li></ul><ul><li>Layer 2 Tunneling Protocol (L2...
CPE-VPNs: IPSec Tunnel Mode <ul><li>IPSec defines IETF Layer 3 security architecture </li></ul><ul><li>Applications - Stro...
CPE-VPNs: IPSec Example <ul><li>Uses normal IP services from service provider </li></ul><ul><li>Protected packets forwarde...
Customer Edge Routers <ul><li>Customer Edge (CE) routers  </li></ul><ul><ul><li>Router or switch device located at custome...
Provider Edge Routers <ul><li>Provider Edge (PE) routers </li></ul><ul><ul><li>Maintain site-specific  VPN Forwarding Tabl...
Provider Routers <ul><li>Provider (P) routers  </li></ul><ul><ul><li>Forward data traffic transparently over established L...
VPN Forwarding   Tables ( VFT ) <ul><li>Each VFT is populated with: </li></ul><ul><ul><li>The forwarding information provi...
VPN  Connection  Tables ( VCT ) <ul><li>The VCT is a subset of information hold by the VFT </li></ul><ul><li>VCTs are dist...
 
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Day5

  1. 1. Network Security and Hacking Techniques Day 5
  2. 2. Introduction <ul><li>Introduction </li></ul><ul><li>What is a Honeypot? </li></ul><ul><li>Value of Honeypot </li></ul><ul><li>Types of Honeypot </li></ul><ul><li>Solutions </li></ul><ul><li>Honeynet </li></ul><ul><li>Etc. </li></ul><ul><li>References </li></ul>“ The Linux Based Service s t hat Mean Business Securing Internet ”
  3. 3. Honeypot <ul><li>The Honepot Project is an all-volunteer, non-profit research organization </li></ul><ul><li>Dedicated to learning the tools, tactics, and motives of the blackhat community and sharing the lessons learned </li></ul><ul><li>Traditional honeypots have been for deception or detecting attacks </li></ul>
  4. 4. Introduction <ul><li>Term originally from the military </li></ul><ul><ul><li>fake target or ambush </li></ul></ul><ul><li>used in network security environment </li></ul><ul><li>Background </li></ul><ul><ul><li>lack of information on blackhat communities </li></ul></ul>
  5. 5. Goal <ul><li>Primary </li></ul><ul><ul><li>an instrument for information gathering and learning. </li></ul></ul><ul><li>other possibilities for a honeypot </li></ul><ul><ul><li>divert hackers from productive system </li></ul></ul><ul><ul><li>catch a hacker while conducting an attack </li></ul></ul><ul><ul><li>etc... </li></ul></ul>
  6. 6. Honeypot (Cont…) <ul><li>1 st Generation Honeypot </li></ul>Firewall separating the Honeynet into three different networks
  7. 7. Honeypot (Cont…) <ul><li>2 nd Generation Honeypot </li></ul>
  8. 8. Honeypot (Cont…) <ul><li>2nd Generation (2002-) </li></ul><ul><ul><li>easier to deploy, yet more difficult to detect </li></ul></ul><ul><ul><li>gather greater information </li></ul></ul><ul><ul><li>all requirements combined onto a single device </li></ul></ul><ul><ul><ul><li>easier to both deploy and manage </li></ul></ul></ul><ul><ul><li>a layer2 gateway, its acts as a bridge </li></ul></ul><ul><ul><ul><li>more difficult to detect (it has no IP Stack) </li></ul></ul></ul><ul><ul><ul><li>control and capture all traffic in the single device </li></ul></ul></ul>
  9. 9. Information Security-Cryptography <ul><li>    Basic Concepts </li></ul><ul><li>    Classical Cryptosystem </li></ul><ul><li>    Mathematics of Cryptography </li></ul><ul><li>    Modern Cryptographic techniques </li></ul><ul><li>    Secret Key Encryption </li></ul><ul><li>    Public Key Encryption </li></ul><ul><li>   Key Management </li></ul><ul><li>Legal Considerations </li></ul>
  10. 10. Information Security-Cryptography <ul><li>Definitions </li></ul><ul><li>Introduction to Crytograhpy </li></ul><ul><li>Example Ciphers </li></ul><ul><li>Types of Ciphers </li></ul><ul><li>Methods of Encryption </li></ul>
  11. 11. Definitions <ul><li>Algorithm: The set of mathematical rules used in encryption and decryption. </li></ul><ul><li>Cryptography: Science of secret writing that enables you to store and transmit data in a form that is available only to the intended individuals. </li></ul><ul><li>Cryptosystem: Hardware or software implementation of cryptography that transforms a message to ciphertext and back to plaintext. </li></ul><ul><li>Cryptoanalysis: Practice of obtaining plaintext from ciphertext without a key or breaking the encryption. </li></ul><ul><li>Cryptology: The study of both cryptography and cryptoanalysis. </li></ul><ul><li>Ciphertext: Data in encrypted or unreadable format. </li></ul><ul><li>Encipher: Act of transforming data into an unreadable format. </li></ul>
  12. 12. Definitions (Conts…) <ul><li>Decipher: Act of transforming data into a readable format. </li></ul><ul><li>Key: Secret sequence of bits and instructions that governs the act of encryption and decryption. </li></ul><ul><li>Key clustering: Instance when two different keys generate the same cipher text from the same plaintext. </li></ul><ul><li>Keyspace: Possible values used to construct keys. </li></ul><ul><li>Plaintext: Data in readable format, also referred to as cleartext. </li></ul><ul><li>Work factor: Estimated time, effort, and resources necessary to break a cryptosystem. </li></ul>
  13. 13. Cryptography <ul><li>The most widely used tool for securing information and services is cryptography. </li></ul><ul><li>Cryptography relies on ciphers: mathematical function used for encryption and decryption of a message. </li></ul><ul><ul><li>Encryption : the process of disguising a message in such a way as to hide its substance. </li></ul></ul><ul><ul><li>Ciphertext: an encrypted message </li></ul></ul><ul><ul><li>Decryption: the process of returning an encrypted message back into plaintext. </li></ul></ul>Encryption Decryption Plaintext Ciphertext Original Plaintext
  14. 14. Example Ciphers <ul><li>Caesar cipher: each plaintext characters is replaced by a character k to the right. </li></ul><ul><ul><li>“ Watch out for Brutus!” => “Jngpu bhg sbe Oehghf!” </li></ul></ul><ul><ul><li>Only 25 choices! Not hard to break by brute force . </li></ul></ul><ul><li>Substitution Cipher : each character in plaintext is replaced by a corresponding character of ciphertext. </li></ul><ul><ul><li>E.g., cryptograms in newspapers. </li></ul></ul><ul><li>plaintext code: a b c d e f g h i j k l m n o p q r s t u v w x y z </li></ul><ul><li>ciphertext code: m n b v c x z a s d f g h j k l p o i u y t r e w q </li></ul><ul><li>26! Possible pairs. </li></ul>
  15. 15. Ciphers <ul><li>For some message M, let’s denote the encryption of that message into cipher text as </li></ul><ul><li>E k (M) = C </li></ul><ul><li>Similarly, the decryption into plain text as </li></ul><ul><li>D k (C) = M </li></ul><ul><li>Notice, </li></ul><ul><li>D k (E k (M)) = M symmetric key algorithms. </li></ul><ul><li>Some algorithms use different keys for each operation: </li></ul><ul><li> D k1 (E k2 (M))= M public-key algorithms. </li></ul>
  16. 16. Simplified Model of Symmetric Encryption
  17. 17. Ingredients <ul><li>Plain text </li></ul><ul><li>Encryption algorithm </li></ul><ul><li>Secret key </li></ul><ul><li>Cipher text </li></ul><ul><li>Decryption algorithm </li></ul>
  18. 18. Requirements for Security <ul><li>Strong encryption algorithm </li></ul><ul><ul><li>Even if known, should not be able to decrypt or work out key </li></ul></ul><ul><ul><li>Even if a number of cipher texts are available together with plain texts of them </li></ul></ul><ul><li>Sender and receiver must obtain secret key securely </li></ul><ul><li>Once key is known, all communication using this key is readable </li></ul>
  19. 19. Attacking Encryption <ul><li>Cryptanalysis </li></ul><ul><ul><li>Relay on nature of algorithm plus some knowledge of general characteristics of plain text </li></ul></ul><ul><ul><li>Attempt to deduce plain text or key </li></ul></ul><ul><li>Brute force </li></ul><ul><ul><li>Try every possible key until plain text is achieved </li></ul></ul>
  20. 20. Cryptanalysis plaintext Encrypt Decrypt K e K d C = E Ke (plaintext) Invader Side information plaintext plaintext Cryptanalysis
  21. 21. Cryptanalysis <ul><li>Cryptanalysis is the science of recovering the plaintext of a message without access to the key. </li></ul><ul><ul><ul><li>Doesn’t have to discover the key necessarily. </li></ul></ul></ul><ul><ul><ul><li>The loss of a key without cryptanalysis is called a compromise. </li></ul></ul></ul><ul><li>Ciphertext-only attack </li></ul><ul><ul><li>The attacker has to recover the plaintext from only the ciphertext. </li></ul></ul><ul><li>Known-plaintext attack </li></ul><ul><ul><li>Portions of the cipher are known as plaintext. The rest may be easier to recover </li></ul></ul><ul><li>Chosen-plaintext attack </li></ul><ul><ul><li>The attacker can choose what plaintext to encrypt, again making it easier to recover other ciphertext. </li></ul></ul>
  22. 22. Encryption Algorithms <ul><li>Block cipher </li></ul><ul><ul><li>Process plain text in fixed block sizes producing block of cipher text of equal size </li></ul></ul><ul><ul><li>Data encryption standard (DES) </li></ul></ul><ul><ul><li>Triple DES (TDES) </li></ul></ul><ul><ul><li>Advanced Encryption Standard </li></ul></ul>
  23. 23. Simple Block Cipher Plaintext message B 2 B 1 B 0 encrypt B 3 B 3 B 2 B 1 B 0
  24. 24. Problem <ul><li>If the same block is encrypted twice with the same key, the resulting ciphertext blocks are the same </li></ul><ul><ul><li>It is desirable to make identical plaintext blocks encrypt to different ciphertext blocks. </li></ul></ul><ul><li>Two methods are commonly used for this: </li></ul><ul><ul><li>CBC mode: a ciphertext block is obtained by first xoring the plaintext block with the previous ciphertext block, and encrypting the resulting value. </li></ul></ul><ul><ul><li>CFB mode: a ciphertext block is obtained by encrypting the previous ciphertext block, and xoring the resulting value with the plaintext. </li></ul></ul>
  25. 25. Stream Ciphers <ul><li>For some applications encryption in blocks will not work </li></ul><ul><ul><li>Telephone conversation </li></ul></ul><ul><ul><li>Radio Broadcast </li></ul></ul><ul><ul><li>… </li></ul></ul><ul><li>White noise… </li></ul>
  26. 26. Stream Cipher encrypt XOR K 0 K 1 K 2 K 3 number generator keystream buffer Plaintext stream Encrypted stream
  27. 27. Data Encryption Standard <ul><li>US standard </li></ul><ul><li>64 bit plain text blocks </li></ul><ul><li>56 bit key </li></ul><ul><li>Broken in 1998 by Electronic Frontier Foundation </li></ul><ul><ul><li>Special purpose machine </li></ul></ul><ul><ul><li>Less than three days </li></ul></ul><ul><ul><li>DES now worthless </li></ul></ul>
  28. 28. Triple DES <ul><li>ANSI X9.17 (1985) </li></ul><ul><li>Incorporated in DES standard 1999 </li></ul><ul><li>Uses 3 keys and 3 executions of DEA algorithm </li></ul><ul><li>Effective key length 112 or 168 bit </li></ul><ul><li>Slow </li></ul><ul><li>Block size (64 bit) too small </li></ul>
  29. 29. Advanced Encryption Standard <ul><li>National Institute of Standards and Technology (NIST) in 1997 issued call for Advanced Encryption Standard (AES) </li></ul><ul><ul><li>Security strength equal to or better than 3DES </li></ul></ul><ul><ul><li>Improved efficiency </li></ul></ul><ul><ul><li>Symmetric block cipher </li></ul></ul><ul><ul><li>Block length 128 bits </li></ul></ul><ul><ul><li>Key lengths 128, 192, and 256 bits </li></ul></ul><ul><ul><li>Evaluation include security, computational efficiency, memory requirements, hardware and software suitability, and flexibility </li></ul></ul><ul><ul><li>2001, AES issued as federal information processing standard (FIPS 197) </li></ul></ul>
  30. 30. AES Description <ul><li>Assume key length 128 bits </li></ul><ul><li>Input is single 128-bit block </li></ul><ul><ul><li>Depicted as square matrix of bytes </li></ul></ul><ul><ul><li>Block copied into State array </li></ul></ul><ul><ul><ul><li>Modified at each stage </li></ul></ul></ul><ul><ul><li>After final stage, State copied to output matrix </li></ul></ul><ul><li>128-bit key depicted as square matrix of bytes </li></ul><ul><ul><li>Expanded into array of key schedule words </li></ul></ul><ul><ul><li>Each four bytes </li></ul></ul><ul><ul><li>Total key schedule 44 words for 128-bit key </li></ul></ul><ul><li>Byte ordering by column </li></ul><ul><ul><li>First four bytes of 128-bit plaintext input occupy first column of in matrix </li></ul></ul><ul><ul><li>First four bytes of expanded key occupy first column of w matrix </li></ul></ul>
  31. 31. AES Encryption and Decryption
  32. 32. AES Comments (1) <ul><li>Key expanded into array of forty-four 32-bit words, w[i] </li></ul><ul><ul><li>Four distinct words (128 bits) serve as round key for each round </li></ul></ul><ul><li>Four different stages </li></ul><ul><ul><li>One permutation and three substitution </li></ul></ul><ul><ul><ul><li>Substitute bytes uses S-box table to perform byte-by-byte substitution of block </li></ul></ul></ul><ul><ul><ul><li>Shift rows is permutation that performed row by row </li></ul></ul></ul><ul><ul><ul><li>Mix columns is substitution that alters each byte in column as function of all of bytes in column </li></ul></ul></ul><ul><ul><ul><li>Add round key is bitwise XOR of current block with portion of expanded key </li></ul></ul></ul>
  33. 33. AES Comments (1) <ul><li>Simple structure </li></ul><ul><ul><li>For both encryption and decryption, cipher begins with Add Round Key stage </li></ul></ul><ul><ul><li>Followed by nine rounds , </li></ul></ul><ul><ul><ul><li>Each includes all four stages </li></ul></ul></ul><ul><ul><li>Followed by tenth round of three stages </li></ul></ul>
  34. 34. AES Encryption Round
  35. 35. AES Comments (2) <ul><li>Only Add Round Key stage uses key </li></ul><ul><ul><li>Begin and ends with Add Round Key stage </li></ul></ul><ul><ul><li>Any other stage at beginning or end, reversible without key </li></ul></ul><ul><ul><ul><li>Adds no security </li></ul></ul></ul><ul><li>Add Round Key stage by itself not formidable </li></ul><ul><ul><li>Other three stages scramble bits </li></ul></ul><ul><ul><li>By themselves provide no security because no key </li></ul></ul><ul><li>Each stage easily reversible </li></ul><ul><li>Decryption uses expanded key in reverse order </li></ul><ul><ul><li>Not identical to encryption algorithm </li></ul></ul><ul><li>Easy to verify that decryption does recover plaintext </li></ul><ul><li>Final round of encryption and decryption consists of only three stages </li></ul>
  36. 36. Location of Encryption Devices Encryption Across a Packet Switching Network
  37. 37. Link Encryption <ul><li>Each communication link equipped at both ends </li></ul><ul><li>All traffic secure </li></ul><ul><li>High level of security </li></ul><ul><li>Requires lots of encryption devices </li></ul><ul><li>Message must be decrypted at each switch to read address (virtual circuit number) </li></ul><ul><li>Security vulnerable at switches </li></ul><ul><ul><li>Particularly on public switched network </li></ul></ul>
  38. 38. End to End Encryption <ul><li>Encryption done at ends of system </li></ul><ul><li>Data in encrypted form crosses network unaltered </li></ul><ul><li>Destination shares key with source to decrypt </li></ul><ul><li>Host can only encrypt user data </li></ul><ul><ul><li>Otherwise switching nodes could not read header or route packet </li></ul></ul><ul><li>Traffic pattern not secure </li></ul><ul><li>Use both link and end to end </li></ul>
  39. 39. Key Distribution <ul><li>Question: How to deliver a shared key to 2 parties that wish to exchange data without others to see the key? </li></ul><ul><li>Key selected by A and delivered to B </li></ul><ul><li>Third party selects key and delivers to A and B </li></ul><ul><li>Use old key to encrypt and transmit new key from A to B </li></ul><ul><li>Use old key to transmit new key from third party to A and B </li></ul>
  40. 40. Automatic Key Distribution for Connection-Oriented Protocols
  41. 41. Automatic Key Distribution <ul><li>Session Key </li></ul><ul><ul><li>Used for duration of one logical connection </li></ul></ul><ul><ul><li>Destroyed at end of session </li></ul></ul><ul><ul><li>Used for user data </li></ul></ul><ul><li>Permanent key </li></ul><ul><ul><li>Used for distribution of keys </li></ul></ul><ul><li>Key distribution center </li></ul><ul><ul><li>Determines which systems may communicate </li></ul></ul><ul><ul><li>Provides one session key for that connection </li></ul></ul><ul><li>Security service module (SSM) </li></ul><ul><ul><li>Performs end to end encryption </li></ul></ul><ul><ul><li>Obtains keys for host </li></ul></ul>
  42. 42. Message Authentication <ul><li>Protection against active attacks </li></ul><ul><ul><li>Falsification of data </li></ul></ul><ul><ul><li>Eavesdropping </li></ul></ul><ul><li>Message is authentic if it is genuine and comes from the alleged source </li></ul><ul><li>Authentication allows receiver to verify that message is authentic </li></ul><ul><ul><li>Message has not altered </li></ul></ul><ul><ul><li>Message is from authentic source </li></ul></ul><ul><ul><li>Message timeline </li></ul></ul>
  43. 43. Authentication Using Encryption <ul><li>Assumes sender and receiver are only entities that know key </li></ul><ul><li>Message includes: </li></ul><ul><ul><li>error detection code </li></ul></ul><ul><ul><li>sequence number </li></ul></ul><ul><ul><li>time stamp </li></ul></ul>
  44. 44. Authentication Without Encryption <ul><li>Authentication tag generated and appended to each message </li></ul><ul><li>Message not encrypted </li></ul><ul><li>Useful for: </li></ul><ul><ul><li>Messages broadcast to multiple destinations </li></ul></ul><ul><ul><ul><li>Have one destination responsible for authentication </li></ul></ul></ul><ul><ul><li>One side heavily loaded </li></ul></ul><ul><ul><ul><li>Encryption adds to workload </li></ul></ul></ul><ul><ul><ul><li>Can authenticate random messages </li></ul></ul></ul><ul><ul><li>Programs authenticated without encryption can be executed without decoding </li></ul></ul>
  45. 45. Message Authentication Code <ul><li>Generate authentication code based on shared key and message </li></ul><ul><li>Common key shared between A and B </li></ul><ul><li>If only sender and receiver know key and code matches: </li></ul><ul><ul><li>Receiver assured message has not altered </li></ul></ul><ul><ul><li>Receiver assured message is from alleged sender </li></ul></ul><ul><ul><li>If message has sequence number, receiver assured of proper sequence </li></ul></ul>
  46. 46. Message Authentication Using a Message Authentication Code
  47. 47. One Way Hash Function <ul><li>Accepts variable size message and produces fixed size tag (message digest) </li></ul><ul><li>Advantages of authentication without encryption </li></ul><ul><ul><li>Encryption is slow </li></ul></ul><ul><ul><li>Encryption hardware expensive </li></ul></ul><ul><ul><li>Encryption hardware optimized to large data </li></ul></ul><ul><ul><li>Algorithms covered by patents </li></ul></ul><ul><ul><li>Algorithms subject to export controls (from USA) </li></ul></ul>
  48. 48. Message Authentication Using a One-Way Hash Function
  49. 49. Public Key Encryption <ul><li>Based on mathematical algorithms </li></ul><ul><li>Asymmetric </li></ul><ul><ul><li>Use two separate keys </li></ul></ul><ul><li>Ingredients </li></ul><ul><ul><li>Plain text </li></ul></ul><ul><ul><li>Encryption algorithm </li></ul></ul><ul><ul><li>Public and private key </li></ul></ul><ul><ul><li>Cipher text </li></ul></ul><ul><ul><li>Decryption algorithm </li></ul></ul>
  50. 50. Public-Key Cryptography
  51. 51. Public Key Encryption - Operation <ul><li>One key made public </li></ul><ul><ul><li>Used for encryption </li></ul></ul><ul><li>Other kept private </li></ul><ul><ul><li>Used for decryption </li></ul></ul><ul><li>Infeasible to determine decryption key given encryption key and algorithm </li></ul><ul><li>Either key can be used for encryption, the other for decryption </li></ul>
  52. 52. Steps <ul><li>User generates pair of keys </li></ul><ul><li>User places one key in public domain </li></ul><ul><li>To send a message to user, encrypt using public key </li></ul><ul><li>User decrypts using private key </li></ul>
  53. 53. Digital Signature <ul><li>Sender encrypts message with their private key </li></ul><ul><li>Receiver can decrypt using senders public key </li></ul><ul><li>This authenticates sender, who is only person who has the matching key </li></ul><ul><li>Does not give privacy of data </li></ul><ul><ul><li>Decrypt key is public </li></ul></ul>
  54. 54. Signatures <ul><li>Handwritten signatures can verify that a document is </li></ul><ul><ul><li>Authentic </li></ul></ul><ul><ul><ul><li>The signature is mine and has not been altered </li></ul></ul></ul><ul><ul><li>Unforgeable </li></ul></ul><ul><ul><ul><li>Proves that I signed the document </li></ul></ul></ul><ul><ul><li>Non-repudible </li></ul></ul><ul><ul><ul><li>I cannot deny that I signed the document </li></ul></ul></ul>
  55. 55. Digital Signatures <ul><li>Public key systems can also be used to provide message authentication: </li></ul><ul><ul><li>The sender’s secret key can be used to encrypt a message, thereby signing it </li></ul></ul><ul><ul><li>This creates a digital signature of a message, which the recipient (or anyone else) can check by using the sender's public key to decrypt it. </li></ul></ul><ul><ul><li>This proves that the sender was the true originator of the message, and that the message has not been subsequently altered by anyone else </li></ul></ul>
  56. 56. Digital Properties <ul><li>The properties of digital documents are different from paper documents </li></ul><ul><ul><li>We need to be able to bind a signature to the entire sequence of bits that make up the document </li></ul></ul><ul><ul><li>How do I prevent someone from revealing their private key and then claiming they never signed something? </li></ul></ul>
  57. 57. Message Digests <ul><li>Message digests are used to create short, fixed-length representations of longer, variable-length messages </li></ul><ul><ul><li>The goal is to make H(M) != H(M’) </li></ul></ul><ul><ul><li>Digest algorithms are designed to produce unique digests for different messages. </li></ul></ul>
  58. 58. Digests
  59. 59. Next Problem <ul><li>You digitally sign a document </li></ul><ul><li>Send the document to a bank </li></ul><ul><ul><li>Encrypted using the bank’s public key </li></ul></ul><ul><li>How do you </li></ul><ul><ul><li>Verify that the public key you used to encrypt the message actually belongs to the bank? </li></ul></ul><ul><ul><li>How does the bank verify that you actually signed the document (or where do they get your public key)? </li></ul></ul>
  60. 60. Certificates <ul><li>A certificate associates a public key with the real identity of an individual, server, or other entity, known as the subject </li></ul>S u b jec t D i s t i n g u is he d N a m e, Pu b l ic K e y Iss ue r D i s t i n g u is he d N a m e, Si g n at u r e Pe ri o d o f v a li d i t y N o t Be f o r e Da t e, No t A f t e r D ate A d m i ni str a t ive i n fo rma ti o n V er si o n , S e r i a l N u mb e r Ex t en d e d I n f or m a t i o n
  61. 61. Certificate Authority <ul><li>A trusted source of certificates </li></ul><ul><ul><li>Verifying certificate requests </li></ul></ul><ul><ul><li>Processing certificate requests </li></ul></ul><ul><ul><li>Issuing and managing certificates </li></ul></ul><ul><li>In previous example </li></ul><ul><ul><li>I would get a certificate for the bank to obtain the public key of the bank </li></ul></ul><ul><ul><li>The bank would get a certificate to obtain my public key </li></ul></ul>
  62. 62. The RSA Algorithm <ul><li>  Key Generation </li></ul><ul><li>  Select p , q p and q both prime, p  q </li></ul><ul><li>Calculate n = p ´ q </li></ul><ul><li>Calculate f( n ) = ( p – 1)( q – 1) </li></ul><ul><li>Select integer e gcd(f( n ), e ) = 1; 1 < e < f( n ) </li></ul><ul><li>Calculate d de mod f( n ) = 1 </li></ul><ul><li>Public key KU = { e , n } </li></ul><ul><li>Private key KR = { d , n } </li></ul><ul><li>Encryption </li></ul><ul><li>Plaintext: M < n </li></ul><ul><li>Ciphertext: C = Me (mod n ) </li></ul><ul><li>Decryption </li></ul><ul><li>Ciphertext: C </li></ul><ul><li>Plaintext: M = Cd (mod n ) </li></ul>
  63. 63. Example of RSA Algorithm
  64. 64. Public-Key Certificate Use
  65. 65. Implementing Network Security using VPNs <ul><li>Introduction to VPNS </li></ul><ul><li>Overview of VPNs </li></ul><ul><li>CPE-Based VPNs </li></ul><ul><li>Provider-Provisioned VPNs </li></ul><ul><ul><li>Introduction to RFC 2547 </li></ul></ul><ul><ul><li>Introduction to CCClLayer 2 MPLS VPN </li></ul></ul><ul><ul><li>lETF Standards Update </li></ul></ul><ul><ul><li>Conclusions </li></ul></ul>
  66. 66. What is a VPN? <ul><li>A private network constructed over a shared infrastructure </li></ul><ul><li>Virtual: not a separate physical network </li></ul><ul><li>Private: separate addressing and routing </li></ul><ul><li>Network: a collection of devices that communicate </li></ul><ul><li>Policies are key — global connectivity is not the goal </li></ul>Shared Infrastructure Mobile Users and Telecommuters Remote Access Branch Office Corporate Headquarters Suppliers, Partners and Customers Intranet Extranet
  67. 67. Deploying VPNs in the 1990s <ul><li>Operational model </li></ul><ul><ul><li>PVCs overlay the shared infrastructure (ATM/Frame Relay) </li></ul></ul><ul><ul><li>Routing occurs at customer premise </li></ul></ul><ul><li>Benefits </li></ul><ul><ul><li>Mature technologies </li></ul></ul><ul><ul><li>Relatively “secure” </li></ul></ul><ul><ul><li>Service commitments (bandwidth, availability, and more) </li></ul></ul><ul><li>Limitations </li></ul><ul><ul><li>Scalability, provisioning and management </li></ul></ul><ul><ul><li>Not a fully integrated IP solution </li></ul></ul>Provider Frame Relay Network CPE CPE DLCI FR Switch DLCI DLCI FR Switch FR Switch
  68. 68. Deploying VPNs in the 21st'Century <ul><li>Uses IP infrastructure </li></ul><ul><li>Can be,shared with Internet services increasing importance of IP/MPLS </li></ul><ul><li>Subscriber benefits </li></ul><ul><li>Lower operational expense </li></ul><ul><li>Single network connection </li></ul><ul><li>Provider benefits </li></ul><ul><li>Multiservice infrastructure </li></ul><ul><li>Creates additional source of revenue </li></ul>Shared Infrastructure Mobile Users and Telecommuters Remote Access Branch Office Corporate Headquarters Suppliers, Partners and Customers Intranet Extranet
  69. 69. VPN Classification Model <ul><li>Customer-managed VPN solutions (CPE-VPNs) </li></ul><ul><ul><li>Layer 2: L2TP and PPTP </li></ul></ul><ul><ul><li>Layer 3: IPSec </li></ul></ul><ul><li>Provider-provisioned VPN solutions (PP-VPNs) </li></ul><ul><ul><li>Layer 3: MPLS-Based VPNs (RFC 2547bis) </li></ul></ul><ul><ul><li>Layer 3: Non-MPLS-Based VPNs (Virtual Routers) </li></ul></ul><ul><ul><li>Layer2: MPLS VPNs </li></ul></ul>PE PE CPE CPE Subscriber Site 3 PP-VPN Subscriber Site 2 CPE PE VPN Tunnel VPN Tunnel VPN Tunnel CPE PE PE PE CPE CPE CPE-VPN VPN Tunnel Subscriber Site 1 Subscriber Site 3 Subscriber Site 2 VPN Tunnel VPN Tunnel Subscriber Site 1
  70. 70. CPE- Based VPN’s
  71. 71. CPE-VPNs: L2TP and PPTP <ul><li>Application: Dial access for remote users </li></ul><ul><li>Layer 2 Tunneling Protocol (L2TP) </li></ul><ul><li>RFC2661 </li></ul><ul><li>Combination of L2f and Point-to-point Tunneling </li></ul><ul><li>Point-to-Point Tunneling Protocol (PPTP) </li></ul><ul><li>Bundled with Windows and Windows NT </li></ul><ul><li>Authentication during setup </li></ul><ul><li>lPSec can operate over PPP for stronger security </li></ul>V.x Modem PPP Dial up Service Provider or 或 VPN L2TP Access Server Dial Access Server L2TP Tunnel Dial Access Server PPTP Access Server PPTP Tunel Dial Access Provider
  72. 72. CPE-VPNs: IPSec Tunnel Mode <ul><li>IPSec defines IETF Layer 3 security architecture </li></ul><ul><li>Applications - Strong security requirements, across one or multiple Service Providers </li></ul><ul><li>Customer responsible for key management </li></ul><ul><li>Security services include: </li></ul><ul><ul><li> Access control </li></ul></ul><ul><ul><li> Data originauthentication </li></ul></ul><ul><ul><li> Replay protection </li></ul></ul><ul><ul><li> Dataintegrity </li></ul></ul><ul><ul><li> Data privacy (encryption/decryption) </li></ul></ul><ul><ul><li>Key management </li></ul></ul>
  73. 73. CPE-VPNs: IPSec Example <ul><li>Uses normal IP services from service provider </li></ul><ul><li>Protected packets forwarded by existing routers </li></ul><ul><li>Does not address QoS/SLAs </li></ul><ul><li>Minimal provider opportunity </li></ul><ul><li>Customer manages its own routing </li></ul>Corporate HQ Branch Office CPE CPE IPsec ESP Tunnel Public Internet
  74. 74. Customer Edge Routers <ul><li>Customer Edge (CE) routers </li></ul><ul><ul><li>Router or switch device located at customer premises providing access to the service provider network </li></ul></ul><ul><ul><li>Layer 2 (FR, ATM, Ethernet) and Layer 3 (IP, IPX, SNA …) independence of the service provider network </li></ul></ul><ul><ul><li>CEs within a VPN, uses the same L2 technology to access the service provider network </li></ul></ul><ul><ul><li>Requires a sub-interface per CE it needs to interconnect to within the VPN </li></ul></ul><ul><ul><li>Maintains routing adjacencies with other CEs within the VPN </li></ul></ul>CE P P PE CE Customer Edge CE CE PE VPN A VPN A VPN B VPN B PE ATM FR ATM FR VPN Site
  75. 75. Provider Edge Routers <ul><li>Provider Edge (PE) routers </li></ul><ul><ul><li>Maintain site-specific VPN Forwarding Tables </li></ul></ul><ul><ul><li>Exchange VPN Connection Tables with other PE routers using MP-IBGP or LDP </li></ul></ul><ul><ul><li>Use MPLS LSPs to forward VPN traffic </li></ul></ul>CE P P PE CE CE CE PE VPN A VPN A VPN B VPN B PE Provider Edge ATM FR ATM FR
  76. 76. Provider Routers <ul><li>Provider (P) routers </li></ul><ul><ul><li>Forward data traffic transparently over established LSPs </li></ul></ul><ul><ul><li>Do not maintain VPN-specific forwarding information </li></ul></ul>CE P P PE CE CE CE PE VPN A VPN A VPN B VPN B PE Provider Routers ATM FR ATM FR
  77. 77. VPN Forwarding Tables ( VFT ) <ul><li>Each VFT is populated with: </li></ul><ul><ul><li>The forwarding information provisioned for the local CE sites </li></ul></ul><ul><ul><li>VPN Connection Tables received from other PEs via iBGP or LDP </li></ul></ul>P P P PE 2 VPN A Site 3 VPN A Site 1 VPN B Site2 VPN B Site 1 PE 1 PE 3 VPN A Site2 CE–A1 CE–B1 CE–A3 CE–A2 CE–B2 P A V FT is created for each site connected to the PE OSPF OSPF OSPF ATM ATM ATM
  78. 78. VPN Connection Tables ( VCT ) <ul><li>The VCT is a subset of information hold by the VFT </li></ul><ul><li>VCTs are distributed by the PEs via iBGP or LDP </li></ul>Site 1 Site 2 Site 1 Site 2 PE-2 CE- 4 PE-1 CE-2 CE- 2 CE-1 VFT VFT VFT VFT A V CT is distributed for each VPN site to PE s MP-i BGP session / LDP
  79. 80. END

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